docs: remove instructions to preinstall SCCache

Author: speednoisemovement

docs/WindowsQuickStart.md

@@ -156,12 +156,9 @@ S:\SourceCache\swift\utils\build.cmd -DebugInfo -SkipPackaging -Test '*'
 
 ### Speeding up the build with sccache
 
-The `-EnableCaching` flag can be used to speed up the build. The
-requirement is that `sccache` is installed and available on the shell
-path. Sccache is available from
-[here](https://github.com/mozilla/sccache/releases). Note that it will
-help speed up the build of the C/C++ code but not the Swift code as
-`sccache` doesn't currently support Swift.
+The `-EnableCaching` flag can be used to speed up the build. This will automatically download
+SCCache before building. Note that this flag will help speed up the build of the C/C++ code
+but not the Swift code as `sccache` doesn't currently support Swift.
 
 ```
 S:\SourceCache\swift\utils\build.cmd -EnableCaching